The present invention relates to a trouble diagnosis system for a motor vehicle.
Recently, a motor vehicle has been equipped with an electronic control system for controlling various components of an engine, such as fuel injectors, thereby improving driveability, exhaust gas emission, fuel consumption, and engine power. The electronic control system controls the components based on information represented by output signals from various sensors for detecting engine operating conditions. Accordingly, if malfunctions of components and sensors occur, the engine does not properly operated.
However, because of the complexity of the electronic control system, it is difficult to immediately find out trouble. Accordingly, a trouble diagnosis device for easily checking the electronic control system should be equipment in an auto shop.
Japanese Patent Application Laid-Open No. 58-12848 discloses a diagnosis system in which a checking device is provided for measuring a pulse duration of fuel injection and an engine speed, and for checking whether idling speed is normal.
However, the system is provided for diagnosing only a designated type of motor vehicle by using an exclusive checking device.
In order to diagnose various vehicles, it is necessary to provide several types of checking devices corresponding to respective types of motor vehicles.
Further, a diagnosis system which stores a plurality of programs for diagnosing various types of motor vehicles has been proposed. In such a system, a code representing a type of an electronic control system provided in a vehicle to be diagnosed must be inputted the diagnosis system. However, it is troublesome work to confirm the corresponding type code and to input the code consisting of a plurality of bits.